If it's smaller, lighter, and has similar IQ to the EF-S 10-22 I actually wouldn't mind... That would also mean having a super portable UWA setup in tight spaces much more possible, for example... video on a jib moving in tight spaces between objects, or those shots when people open up a box or bag and the angle is coming from the inside. When you do photo or video work in tightly spaced venues it makes a lot of sense. It opens up a lot of creative possibilities, and is generally more flexible in terms of practical features compared to let's say... a gopro. The portability is already awesome for backup (with adapter) and vacation use. It also means you can carry lighter tripods and etc. Eliminating the need for the adapter in different ranges makes it even lighter and smaller.

I have a M and it's bloody marvellous ! With the 22mm pancake, it's light for hill walking, pictures from it are great, it looks like a cheap compact to a hit and run thief... And importantly, gets the important capture of your life when the FF + f2.8 is just too heavy or big or expensive looking to carry along.

I agree with @ecka... IS (nowadays) is more of a feature for amateur video more so than still photos. I wouldn't take serious landscape or architectural photos hand holding my camera at 1/15s, although just having that ability helps.